SAO SETA Kick-Off by HC120831084028

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									Alaska Sources of Control – SDMI Task 4
          Goal & Approach
• Conduct a survey of existing control
  sources.
• Public and private sources that could be
  acquired for Alaska utilization.
• Separate existing image identifiable
  content
• Also gather pragmatic feedback from
  existing practitioners
• Produces maps and report
     Just because you’ve got it
doesn’t mean it’s the right fit for the job
       What is the Application
– Geodesy, Costal, Civil Engineering?
– Aviation?
– Control imagery?
   • 1:24k NMAS
  • EO or RaDAR
– Correlate with other datasets?
  • Change detection, veg mapping, EIS?
– Control DEM?
– Validate imagery or DEM?
– Control collection platform?
45km Populated Places Buffers
      Approx. 63% of Alaska
45km Runway Buffers
 Approx. 63% of Alaska
           Some Variables
– Desired map scale / accuracy of output
  products
– Interaction with other input components
– Error budget
– Image identifiability
– Orientation related to area of mapping
– Stability over time (seasons and years)
– Costs of collection
– Access
– Costs of utilization
            Approximate Map Scale
                Equivalencies


Map Scale   CE90    RMSE     1-Sigma

1:50,000    25.4m   15m      12m

1:24,000    12.2m   6m       3m

1:12,000    10.2m   5m       2m

1:4,800     4.1m    2m       2m

1:2,400     2.0m    1m       1m
   Imagery Ortho Error Budget
• Many factors contribute to the overall
  accuracy of map product
  – DEM
  – Incidence angle, sensor to ground
  – GCP
  – Sensor design
  – Orbital Position Estimation
  – AGPS & IMU / Pointing Accuracy
  – Block size
DEM Accuracy is Significant Error
  Source for Imagery Location
Error Budget Calculations
           GCP Accuracy
• Keep mapping scale in mind
• 1:24K means a 0.1mm thick line is
  2.4m wide on the ground!
• To achieve NMAS, >90% of all
  sample points must fall less than 40
  feet (12.19m) from ground truth
           GCP Accuracy
• Most modern survey grade GNSS
  receivers capable of +/- 5mm +
  0.5ppm (1 sigma)



• CORS may provide sufficient
  coverage if SDMI requirements are
  1:24,000
CORS Availability
Alternatives to CORS - UNAVCO
   Alternatives to CORS
• TerraPOS – uses precise GPS
  satellite ephemeris
            GPS and GNSS
• Raise elevation mask 2⁰/100km from base
  to ensure common satellites observed
• If possible, use a GNSS receiver rather
  than straight GPS – better for mountains
              Satellite Imagery as Control
                           (all CE90)


Sensor            Native Radial Accuracy   Improved Accuracy

SPOT 5            39m                      15m w/ Ref3-d

IKONOS            15m

Quickbird         23m

WorldView-1       6.5m modeled             3m – 5m actual

GeoEye-1          5.0m modeled             4m stereo,
                                           expect 2-5m mono actual

								
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